A correct approach to slide examination is considered crucial for an appropriate interpretation of cytological samples and to reduce the chances of missing important details. A poor and superficial examination technique may lead to a wrong diagnosis and incorrect clinical decisions. Therefore, cytological evaluation should be performed with a systematic approach, conducted in the same way each time a slide is examined.
The overall accuracy of cytology testing greatly depends on the quality of the specimen, including the cellularity of the sample, the preservation of the cells and the quality of the staining.
• Inadequate sampling or smearing technique.
• Excessive suction.
• Traumatic smearing.
• Haemorrhagic lesions.
• Aspiration from a necrotic centre.
• Poorly exfoliative lesions (e.g. lesions rich in collagen stroma).
• Staining features.
• Insufficient staining due to incorrect procedure or old stains.
• Sample contamination with lubricant or ultrasound gel.
• Exposure of the unfixed slides to formalin fumes.
When the aspirates are acellular or mostly contain disrupted cells without a clear and distinct cytoplasm (e.g. bare/naked nuclei), a cytological interpretation may not be possible and re-sampling should be recommended. Similarly, if the sample is adequately cellular and the cells are intact but the staining quality is poor, a cytological diagnosis might be precluded.
3.1 Step-by-step Approach to the Slide Examination and Description
Step 1: Low-power magnification (4×, 10×, 20×)
Smears should initially be scanned with low-power objectives to gain an appreciation of the overall cellularity and cell preservation. It is important to examine the entire smear, including the feathered edges.
The following points should be considered when examining a cytology smear at low magnification:
• Is the cellularity adequate for the type of specimen and collection technique? Is it enough to attempt a diagnosis?
• Are the cells adequately stained and well preserved?
• Is there any non-cellular background material that may be of significance, such as matrix, cytoplasmic fragments (lymphoglandular bodies), etc?
• Is there a monomorphic or a mixed population of nucleated cells? Are these homogenously distributed throughout the smear?
• Is there evidence of any typical cell arrangement and/or cytoarchitecture?
• What types of cells are present (e.g. inflammatory cells, tissue cells, or a mixture of the two)?
Step 2: High-power magnification (40×, 50×, 100×)
High magnification allows for a more detailed evaluation of the cell morphology details.
• Inflammatory cells
The inflammatory process should be classified based on the predominant cell type/types. The morphology of the inflammatory cells should be carefully examined for the presence of significant changes, such as degenerative changes in the neutrophils or phagocytic activity by the macrophages, etc.
• Infectious agents
When appropriate, a thorough examination of the slides for the presence of infectious agents (bacteria, fungi, protozoa, etc.) should be made. Bacteria are usually found in the background of the smears and/or phagocytosed by the neutrophils. Fungi and yeasts are usually found in the background, surrounded by the inflammatory cells, or within macrophages. When a fungal infection is suspected and the aspirates are highly cellular, hyphae are usually hidden amongst the inflammatory cells in the thickest areas of the smear. Protozoa are generally found within macrophages.
• Tissue cells
These can be classified into epithelial, mesenchymal or round cells based on their arrangement and morphology.
When writing a cytology report, the shape and arrangement of the cells, morphology of the nucleus and cytoplasmic features should be described.
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
